The invention relates to a balance system, in particular to a balance state indicator for a movable barrier operator.
Most known movable barrier operators, or garage door operators include a motor having a transmission connected to it, which is coupled to a barrier for opening and closing the barrier. With a vertically moved barrier, there are normally preset upper and lower limits of travel. The upper and lower limits are employed to create a safe operational travel range.
Balance springs are often attached to a vertically moving barrier to offset the weight of the door. This is an aid to human barrier movers as well as the motor of automatic barrier movers. Other types of door balancing arrangements are known but infrequently used. Balance springs may be torsion springs, which mounted above the barrier opening on a shaft which rotates. The balancing force of the torsion springs is generally conveyed to the barrier by flexible members such as cables, which take up or pay out on drums attached to rotate with the torsion spring shaft. In other arrangements, the balance springs may be expansion springs, which are stretched when the barrier is lowered and contract when the barrier is raised. The expansion springs are commonly attached above barrier guide tracks and connect to the barrier by flexible members running over pulleys.
In the case of garage door systems the amount of spring tension to balance the door is determined by the amount of balance spring tension to hold the barrier at about three to four feet above the floor. That is, a properly balanced garage door would stay in the half open position. If the door closes by itself, the springs require more tension. If the door opens by itself, the door springs have too much tension. As the garage door system ages, or part of the balance system breaks, the balance may deviate. The door balance may deviate to a point at which it is extremely difficult or dangerous to continue to operate the door. However, due to the robustness of door operators, the out of balance condition may go unnoticed by human operators who merely push control button to open and close the door. Thus, there is a need for a balance system that would be able to determine when the garage door system passes its imbalance threshold and notify the owner that the garage door is out of balance.